Hmm. Well, I'm going to be pedantic (what a shock) and first question the definition of "hot". If we're talking purely appearances, I'd say probably either Sanji or possibly Fullbody in terms of my aesthetics. Kohza and Wiper are up there, too. Zoro… has been a little difficult for me to tell exactly how attractive he's meant to be. To paraphrase someone else, I always sort of pictured him as the sort of man who, if he were a woman, would have an abundance of unwanted body hair, a not unattractive but not conventionally-good-looking face, with a really smokin' body. Having said that, I have no real concrete reasons for thinking so other than just a gut reaction. I don't think he's ugly, I just don't think he's probably particularly good-looking, either.
Having said that, attitude and personality count for a lot, at least for a lot of the ladies (and guys, I'm sure). In that effect, the only members of the main cast I don't find attractive would be Luffy and Chopper, and partially for the same reason-- they're so young. Physically they're not that young (I think Chopper's supposed to be 15), but emotionally they're still in single digits, which automatically makes them sexual non-entities as far as I'm concerned. Chopper's also got that whle animal thing going on, which shoves him further out.
But most male characters have personalities that appeal to me in some fashion-- hell, I happen to think Cricket's pretty hot, despite the fact that his features do nothing for me aesthetically. It's all very subjective.
(Ugh, my psych class is really not helping me get any shorter-winded.) But in essense, Sanji's the one I tend to find most attractive-- after being involved with men who are pretty much the antithesis of his attitudes and ideals and having had to go through a lot of crap because of it, I'm pretty much ruined on guys who aren't like Sanji at least a fair amount. Interestingly, until relatively recently, Sanji was even more ambiguous to me in terms of physical attractiveness than Zoro. I really couldn't decide (especially in the early chapters) if he was supposed to be attractive or not. Lately it seems obvious from the way Oda draws him, but for quite a while there it could have gone either way.
Finally done talking.